Methods to Determining Cleanliness in Parts Washing

pharmaceutical beakers and test tubes

In many industries, parts need to be cleaned thoroughly before or after being manufactured, during a production process, or before being used to process a new batch of material. Automatic parts washers are often used to insure that parts are cleaned precisely. But how can you be sure that your parts are really clean? What are the methods to determine parts washing cleanliness? The following are just a few of the methods used to assess if a part is actually clean:

Water-Break Test:
Water will sheet off the part rather than bead
  • Take a cleaned and dried part and set it in a vertical position
  • Use a spray bottle containing distilled water
  • Spray the part two to three times from at least 6″ away
  • The water spray should sheet off if the part is clean and free of oily residue
  • The water will tend to bead on the part if some oily residue remains
UV Black Light:
Can you see fluorescence on the parts when viewed using a black light?
  • Take the cleaned and dried part and the black light into a dark area
  • In the dark area, shine the black light onto the part 
  • It should not highlight any fluorescence if the part is free of soils
  • You should see some florescence where the soil is present if some soil remains
  • You should check a dirty part for florescence to ensure that the soil emits a florescence when viewed under a black light
Clean-wipe test:
Will a white cloth remain white after being rubbed on the cleaned part?
  • Take the cleaned and dried part and wipe it with a portion of a clean, white, lint-free cloth. 
  • The part is sufficiently clean if the cloth remains clean
  • The part still contains soil residue if the cloth becomes soiled or discolored
Gravimetric testing:
Will tell how much contaminate is left on the part
  • Involves filtering a contaminated sample through a control filter and a sample filter
  • Place two pre-weighed filters, one on top of the other in a single filter holder
  • Sample contaminants will be retained entirely by the top test filter
  • Both filters are subjected to identical alterations in tare weight as a result of moisture
  • Any change in weight of the bottom (“control”) filter is then applied as a correction to the weight of contaminant
  • Results accurate to 0.1 mg are routinely attained using this method

Better Engineering uses these methods and more to assess and insure the proper cleanliness in the parts washing process. BE has a full engineering lab and machine demonstration center to test clean your parts according to your application. For a complimentary parts washing consultation, contact Better Engineering via email or phone at 1-800-229-3380.



60 Years Experience


BE develops innovative solutions to build critical automated cleaning systems for virtually every industry.

female engineer in factory

Our services

Comprehensive support for all of your cleaning solution needs!